type IOther = "sing" | "dance" | "rap";

// extract 从联合类型中提取指定的类型
type ExtractType<T, E> = T extends E ? T : never

// 变成可选的
type IOtherOptional = ExtractType<IOther, "sing" | "rap">;

const otherOptional: IOtherOptional = "sing";

export {}
